In 1922 Sigmund Freud wrote to Arthur Schnitzler, the Austrian playwright known for his penetrating psychological dramas, to congratulate him on reaching his sixtieth birthday. In this letter Freud asked himself why, for so many years, he had avoided meeting a fellow Viennese intellectual whose ideas he so esteemed for their similarity to his own. In answering this question, Freud offered “a confession” to Schnitzler—one that he requested the playwright to keep to himself. “I think I have avoided you from a kind of reluctance to meet my double [Doppelgängerscheu]…. Whenever I get deeply interested in your beautiful creations I always seem to find behind their poetic sheen the same presuppositions, interests and conclusions as those familiar to me as my own.”1

Freud was ambivalent about meeting his Viennese doppelgänger because, like most scientists, he was intensely concerned about scientific priority, raising this concern more than 150 times in his correspondence and published works. According to the sociologist Robert K. Merton, who documented Freud’s intense preoccupation with securing his own claims to originality, ambivalence is a hallmark of the way scientists feel about having scientific priority.2 Merton even declared, as a rule of thumb, that whenever the biography or autobiography of a scientist states that he has had little interest in being the first, one is likely to find, within a few pages, one or more references to his having been embroiled in controversy over this very issue.

1.

“I Never Saw a More Striking Coincidence”

If ever a famous scientist was unexpectedly confronted by his intellectual double—a colleague whose independent discovery of the same revolutionary idea threatened to undermine his prospects for scientific immortality—that scientist was Charles Robert Darwin (1809–1882). The man who threatened Darwin with losing his place as an original thinker was another British naturalist, Alfred Russel Wallace (1823–1913). Living in the jungles of the faraway Malay Archipelago, Wallace was diligently collecting tens of thousands of natural history specimens when he experienced, in February 1858, one of many recurrent attacks of malarial fever. While he was incapacitated and in a state of intermittent delirium, Wallace found himself mulling over the relentless destructive forces in nature that keep natural populations from increasing in size. Wallace suddenly recalled the argument of Thomas Robert Malthus’s Essay on the Principle of Population (1826), in which Malthus had maintained that human populations tend to increase at a geometric rate whereas the food supply tends to increase only at an arithmetic rate. According to Mal-thus, the inevitable consequence of this mathematical discrepancy was the existence of powerful “checks” to population increase. It then flashed across Wallace’s mind, as it had Darwin’s when he read the same book by Malthus twenty years earlier, that only the fittest and most adapted individuals would tend to survive in nature, and hence that a process of natural selection would cause new and better-adapted varieties to replace older and inferior ones.

When his malarial attack had subsided, Wallace quickly sketched out his theory and dispatched his manuscript to none other than Darwin, with whom the younger naturalist had previously corresponded. Upon receiving this manuscript, Darwin, who was busy writing his own “Big Book” on species, was stunned by what he read. As he explained to his close friend the geologist Charles Lyell:

Your words have come true with a vengeance that I should be forestalled. You said this when I explained to you here very briefly my views of “Natural Selection” depending on the Struggle for existence.——I never saw a more striking coincidence. [I]f Wallace had my M.S. sketch written out in 1842 he could not have made a better short abstract! Even his terms now stand as Heads of my Chapters…. So all my originality, whatever it may amount to, will be smashed.

Darwin agonized over what to do, thinking that the only honorable course of action was to step aside and yield to Wallace, but he gladly acquiesced in the solution proposed by his two closest scientific colleagues—the botanist Joseph Dalton Hooker and the geologist Charles Lyell. In what has been referred to as a “delicate arrangement,” Darwin’s two friends oversaw the publication of Wallace’s paper, preceded by portions of an unpublished essay that Darwin had written in 1844, and by a letter summarizing his theory, which Darwin had sent to the American botanist Asa Gray in 1857. Darwin’s scientific priority was thereby assured. In part because of this delicate arrangement, we now describe modern evolutionary theory as “Darwinian” rather than “Wallacian.”

The life stories of these two scientific doppelgängers, their extraordinary intellectual accomplishments, and their even more extraordinary discovery of the same cornerstone of evolutionary biology have now been retold in two new and eminently readable biographies. Janet Browne starts the second and concluding volume of her superb life of Darwin with that dramatic moment in June 1858 when Darwin received Wallace’s manuscript anticipating his theory of natural selection. The life of Darwin’s intellectual double has been comprehensively chronicled by Michael Shermer in his provocative study about the scientist who was content and even flattered to live “in Darwin’s shadow.” Although Darwin and Wallace may have been scientific doubles, their latest biographers are clearly not, taking very different methodological approaches to their subjects based on disparate conceptions of what makes for good history and good biography.

Janet Browne’s Charles Darwin: The Power of Place is a commendable successor to Charles Darwin: Voyaging (1995), in which Browne tells the story of Darwin’s five-year voyage around the world on H.M.S. Beagle (1831– 1836), his conversion to evolutionary theory and subsequent discovery of the principle of natural selection, and finally his prolific pre-Origin contributions to natural science, which grew out of his Beagle voyage exploits. Browne’s second volume follows Darwin through the storm of controversy over the Origin of Species (1859) and then takes us through the remarkable diversity of his later achievements, which included The Descent of Man (1871) and The Expression of the Emotions in Man and Animals (1872), as well as pioneering books on orchids, variation in domesticated animals and plants, insectivorous plants, the evolutionary implications of flower structure, and a best-selling work on earthworms.

Lavish and justified praise has been bestowed on the first volume of Browne’s study. There can be no doubt, however, that her second volume is an even more important contribution to Darwin studies, and, among other accolades, it has received the National Book Critics Circle Award for biography. The importance of Browne’s second volume lies substantially in the fact that less is known and properly understood about Darwin’s later life, mainly because the volume of relevant documentation for Darwin’s years as a scientific celebrity is far greater, and far more diverse, than the already formidable material associated with the first five decades of his life.

What is particularly new about Browne’s approach to Darwin is her ability to place him and his scientific research within the real-life, day-to-day setting provided by his wife and family, by the small town in which he lived sixteen miles south of London (and where he served as a local magistrate, handing out pig licenses and administering fines for poaching), and by the broader mix of friends, colleagues, and celebrity seekers with whom he was in touch during the last two decades of his life.

Especially fascinating is Browne’s detailed reconstruction of Darwin’s emotional life. In fact, Browne’s biography has brought Darwin alive for me in ways that I, as someone who has studied Darwin’s life for more than thirty years, had not thought possible from the available documentary evidence. Browne’s achievement is testimony not only to her diligence in locating and judiciously mining new sources—particularly family letters—but also to her ability to exploit the previously known documents in new and fruitful ways. Owing to Browne’s perceptiveness and gifts as an author, she often writes more like a novelist than a biographer. Of course, the best biographies do sometimes read like good novels, but achieving this result with a life dedicated to science entails another degree of literary skill altogether.

In contrast to Desmond and Moore’s 1991 biography of Darwin, in which Darwin is portrayed as a tormented victim of his own relentless fears about betraying his conservative, upper-class friends and colleagues,3 Browne’s Darwin emerges as a much more self-confident man—someone who skillfully managed his various apprehensions about his work by employing multiple strategies designed to further the Darwinian revolution. Toward this end, the second volume of Browne’s biography is organized into three parts: “Author,” “Experimenter,” and “Celebrity.” The most powerful theme of her narrative, however, transcends these temporal markers of Darwin’s life and work and chronicles Darwin’s abilities as a tactician. At least four different kinds of strategies (literary, collaborative, social, and experimental—although not all explicitly identified as such by Browne) governed Darwin’s successful orchestra- tion of the revolution in science that now bears his name.

2.

Darwin as Master Tactician

Darwin’s various literary strategies were largely built around his monumental correspondence, which relentlessly drove his science forward by supplying him with facts on almost every conceivable subject that he needed for his research. Darwin wrote or received more than 14,000 letters preserved in libraries around the world, and many more such letters have been lost. The projected size of Darwin’s published correspondence, now being edited by Frederick Burkhardt, Duncan M. Porter, and others, is more than thirty volumes.4 After 1871, when The Descent of Man was published, Darwin appears to have written about 1,500 letters a year (about four letters every day), and he received a similar number in return.

By 1877 he was spending a yearly sum on postage and stationery that was roughly equal to his butler’s annual salary. In addition to a copious correspondence with fellow scientists, there were numerous letters to and from fur trappers, zookeepers, gardeners, farmers, pigeon fanciers, and many other kinds of breeders. This prodigious correspondence, Browne emphasizes, “characterized the heart of Darwin’s scientific undertaking…. With pen and ink and postage stamps he set about constructing what he hoped would be ‘a considerable revolution in natural history.’” So eager was Darwin for letters that we are told he even installed a mirror on his study window so he could catch the first sight of the postman walking up the driveway.

By means of this extensive correspondence, which took Darwin several hours a day, he used his position at the top of the scientific hierarchy to induce his many correspondents to supply him with endless facts and even to undertake entire research projects on his behalf. A year before Wallace sent Darwin his bombshell essay from the Malay Archipelago, Darwin had asked the younger naturalist to send him skins of any unusual Indonesian poultry, as well as information on the mating of jaguars and leopards, parrots that change color after eating fish, and the means of dispersal of animals and plants that inhabit oceanic islands. Other correspondents were expected to conduct matings between different breeds of domestic fowl and to dutifully report the results back to him. “I am a complete millionaire in odd and curious little facts,” Darwin informed Hooker, with many such useful letters in hand while he was writing his two-volume Variation of Animals and Plants under Domestication (1868).

Darwin’s literary strategy extended effectively to his published prose. Browne details how Darwin shrewdly shaped his image in the Origin of Species by adopting a modest, autobiographical style that produced “a distinctive magic between author and reader.” For example, Darwin made frequent confessions about the most serious scientific problems confronting his overall argument, claiming, for instance, that “to this day I can never reflect on them without being staggered.” Darwin’s chapter “Difficulties on Theory” was so forthright, in fact, that Wallace actually thought Darwin had gone too far in providing ammunition to his critics, for instance by emphasizing how extremely hard it was, even for Darwin, to imagine that natural selection could ever have created so complicated an organ as the eye. Owing to such intellectual probity, however, Darwin’s reputation as an earnest and honest thinker assumed a commanding presence distinct from his often shocking theories, paving the way for his eventual interment, twenty-two years later, in Westminster Abbey.

For people who were within Darwin’s immediate orbit of family and friends, the kinds of written requests that he made to scientific colleagues were replaced by frequent enticements to collaborative assistance. Every family relation, and even the household pets, were fair game for being incorporated into Darwin’s scientific enterprise. His wife, Emma, and eldest daughter, Henrietta, provided him with extensive editorial assistance with the Origin and later works, from proofreading galleys to rewriting his prose and sometimes influencing the structure of his scientific arguments. His children, especially his sons, were often enlisted in his researches, as were his various sons- and daughters-in-law, his nieces and nephews, and his cousins.

Together these extended family members helped Darwin to determine such arcane facts as the flight path of the male bumblebee and whether earthworms can hear the sound of a bassoon. In 1874, Darwin’s twenty-five-year-old son, Francis, became his full-time assistant and secretary, and was a silent coinvestigator in most of Darwin’s subsequent botanical research. Francis, who developed into a distinguished botanist in his own right, also edited Darwin’s three-volume Life and Letters (1887), which included Darwin’s autobiography, as well as two volumes of More Letters (with A.C. Seward, 1903). These hagiographic works consolidated Darwin’s historical image for the next century. So closely entwined was Darwin’s family in his researches that the line between science and family often blurred. Darwin was fond, for example, of referring to his theories as his children and to himself as their father.

Darwin also emerges in Browne’s biography as a person who was effective socially, working behind the scenes, to bring about a desired end. His appeal to Hooker and Lyell regarding the issue of his priority over Wallace was just one instance in which he played his cards deftly, getting his friends to do for him what he felt he could not, as an honorable gentleman, do for himself. Similarly, Darwin worked diligently to promote the most skilled defenses of the Origin, by republishing particularly favorable articles about his work and by arranging for translations of books that defended him the best.

In fact, promotion of the Origin became what Browne calls “the directing theme” of Darwin’s life after 1859. In this regard his mysterious illness, which kept him from attending public battles over his controversial theories, often stood him in good stead, because it saved him time and emotional distress while allowing his loyal lieutenants, such as J.D. Hooker and Thomas Henry Huxley, to earn the praises of an ever-grateful scientific patriarch who selectively bestowed favors on those disciples who came to his aid. For the impecunious Wallace, who selflessly promoted the term “Darwinism” in reference to his own and Darwin’s theory of evolution, Darwin arranged a life pension from the government. Similarly, Darwin collected £2,100 from fellow scientists (worth roughly $150,000 today) so that Huxley—who was on the verge of a nervous collapse from financial problems and overwork—could take some time off.

Darwin’s fourth and last talent as a master tactician involved his distinctive abilities as an experimentalist, often working with the most primitive of tools. What the Beagle voyage was for Darwin during the first third of his life, and what his correspondence was for him in the middle third, experimental research became for him during the last third. Darwin seems to have discovered the power of experiments as he glimpsed, after the Beagle voyage, the extensive terra incognita of unanswered questions that his evolutionary theories had opened up for research. The naturalist who had once circumnavigated the world, exploring the global record of natural experiments in time and place, could now sail conceptually through many other unexplored scientific domains from the comfort of his own home. Whether he was soaking seeds in salt water to see if they could survive transport by sea currents to remote oceanic islands or pollinating plants by hand to demonstrate the hybrid vigor that occurs from cross-fertilization, Darwin was increasingly in his creative element owing to these kinds of adventures of the mind.

It is hard to find fault with Browne’s remarkably sensitive and well-written portrait of Darwin’s life without criticizing her for the book she chose not to write. It is perhaps fair to say, however, that Browne’s perceptive immersion in the day-to-day details of Darwin’s family life and scientific work, while indeed demonstrating the far-reaching “power of place” in his home-based scientific achievements, leaves unanswered some of the most difficult questions about Darwin’s life and accomplishments. One senses that she felt her successful emulation of a novelist’s style might have been hampered by too much analysis.

One example is Browne’s reluctance to take a position on the causes of Darwin’s mysterious illness, or even to present the arguments for or against the various theories on this subject. In this reviewer’s opinion—given new information that has emerged in the last few years about the various forms and stages of Chagas’ disease—Darwin indeed appears to have contracted this parasitic disorder during the Beagle voyage after being severely bitten in South America by the principal carrier, known as the vinchuca or “assassin bug.”5 The most common symptoms of Darwin’s illness—nausea, vomiting, and flatulence—are precisely those found in a substantial portion of the victims of this disease, which attacks and injures the parasympathetic nerves of the intestines and also sometimes damages the heart. If anyone has the boldness to disinter Darwin at Westminster Abbey, a definitive test is now available to answer this question thanks to the amplification of DNA by the method of polymerase chain reaction (PCR).6 In addition to having Chagas’ disease, a good argument can also be made that Darwin suffered from various psychosomatic symptoms (and perhaps an anxiety disorder) during times of high stress in his life. In any event, given the forty-two years that he spent suffering extensively from his mysterious disorder, Darwin would surely have wished for a more informative discussion of this subject if he were reading Browne’s fine biography for himself.

I think Darwin would also have yearned to know the answer to several other general questions that are only briefly or tangentially touched upon in Browne’s book, including the really big one that Stephen Jay Gould posed in his review of the first volume of Browne’s biography in this same publication—namely, “Why Darwin?” Why, that is, was Darwin so remarkably successful in science?7 It is nevertheless testimony to Browne’s impressive achievement that the answer to this and other intriguing questions about Darwin’s life and thought must inevitably draw heavily on the portrait that she has so painstakingly created of the country squire who, from his house and surrounding gardens, transformed the thinking of his age.

3.

An Unlikely Doppelgänger

One of the impressive features of Michel Shermer’s “dazzling new biography” of Alfred Russel Wallace (as Janet Browne herself describes it on the jacket) is that it reveals the full paradox of Wallace’s doppelgänger status vis-à-vis Darwin. The temptation has always been to make the most of the similarities between these two naturalists, an approach Wallace himself took toward the end of his life. As he pointed out in 1908, both men had been “ardent beetle-hunters” in their youth; both subsequently had become travelers, collectors, and observers in some of the most remote parts of the world; both were drawn to asking the big “why” questions (such as why there is so much variety in nature); and both had read Lyell’s Principles of Geology and Malthus’s Essay on Population. According to Wallace, these similarities acted like “friction upon the specially-prepared match,” eliciting the “flash of insight” that led each of them to their theory about the survival of the fittest.

What we see from Shermer’s biography, however, is just how different these two men were in so many crucial ways that profoundly affected their scientific thinking. Unlike Darwin, who came from a well-to-do family, Wallace grew up in difficult economic circumstances and received only seven years of formal schooling (making his subsequent achievements in science all the more astonishing). For Wallace there were no well-placed mentors, like Darwin’s teacher John Stevens Henslow, who could procure for him an invitation to sail around the world on a British naval vessel. Instead, Wallace worked for a time as a surveyor, finally saving enough money (about $7,500) to risk it all on a self-organized collecting venture to the Amazon basin, from 1848 to 1852, with his friend Henry Walter Bates, followed by another even more extensive collecting expedition, from 1854 to 1862, to the Malay Archipelago. Compared with Darwin, who sailed on a ninety-foot brig in relative comfort (at least when he wasn’t seasick), Wallace traveled on smaller and sometimes unsafe ships, by canoe, or on foot through 34,000 miles of dangerous jungles, where he was afflicted with malaria, dysentery, and yellow fever—the disease that killed his younger brother, Herbert, not long after he had joined Wallace in the Amazon as his assistant. The vessel on which Wallace returned from the Amazon to England, in 1852, caught fire and sank seven hundred miles from Bermuda. Barely escaping with his life, Wallace lost most of his scientific notes, journals, and specimens.

Whereas Darwin enjoyed family wealth and used it to great advantage to support his science, Wallace was so poor throughout his later scientific career that he even worked for Charles Lyell, in secret, for five shillings an hour (today’s equivalent of twenty dollars). Also unlike Darwin, the ever- trusting Wallace was hapless in financial matters, losing in bad investments what little money he was able to save. Wallace nevertheless survived all of this adversity owing to an astonishing physical and literary energy, which resulted in his collecting more than 125,000 specimens in the Malay Archipelago alone and turning out 769 lifetime publications, including twenty-two books. Besides his many insightful contributions to evolutionary theory, he published pioneering work on the geographic distribution of species and on island biogeography. He was, as Shermer comments at one point, “a veritable scientific and literary engine,” writing on boats and in primitive field camps without adequate library resources and sending manuscripts by steamship and hoping for the best.

Just as Wallace’s life differed dramatically from that of his gentlemanly doppelgänger, his theories did as well. It is in attempting to understand the salient features of Wallace’s scientific worldview that Shermer’s biography really shines. Shermer’s main concern is to explain Wallace’s ideas about the evolution of human beings, which have long puzzled historians of biology. In the mid-1860s Wallace came to believe that natural selection could not possibly account for the evolution of the human body (for example, the trait of hairless skin, which Wallace thought to be maladaptive) or the evolution of the human mind (for instance, the ability to engage in higher mathematical reasoning). In Wallace’s view, natural selection “could only have endowed the savage with a brain a little superior to that of an ape, whereas he actually possesses one but very little inferior to that of the average members of our learned societies.”

In the face of such seemingly inexplicable mental and physical attributes, Wallace came to the conclusion that spiritual forces, normally unseen but detectable by skilled mediums, had guided human evolution to a higher level and would continue to do so in the future. It was these heterodox views that prompted a disappointed Darwin to declare to Wallace in 1869: “I hope you have not murdered too completely your own and my child.”

4.

Darwin’s Dictum as Biographical Guide

In addressing the question of why Wallace chose to deviate from the Darwinian status quo that he was so instrumental in helping to create, Shermer interweaves his story with insights based on the concepts and methods of science—particularly those drawn from psychology. This aspect of his biography, which contrasts with Janet Browne’s narrative approach to social history, is its most intriguing and controversial feature. Shermer premises his call for scientific biography on what he calls “Darwin’s dictum,” contained in a comment that Darwin made in 1861 about the relationship between theory and observation:

About thirty years ago there was much talk that geologists ought only to observe and not to theorise; and I well remember someone saying that at this rate a man might as well go into a gravel-pit and count the pebbles and describe the colours. How odd it is that anyone should not see that all observation must be for or against some view if it is to be of any service!8

Facts, even biographical and historical facts, Shermer agrees with Darwin, must always be interpreted through the lens of theory. In articulating this scientistic viewpoint, Shermer strongly reflects his own personal background as editor of Skeptic magazine (which is largely dedicated to debunking pseudoscience), his role as a columnist on “borderland” science for Scientific American, and his perspective as the author of Why People Believe Weird Things.9

One tack in Shermer’s appeal to scientific guidance involves his asking ten experts (including the author of this review) to rate Wallace’s personality. Wallace, for example, was judged to be in the 86th percentile in a test measuring “Openness to Experience,” an aspect of personality that psychologists consider most directly relevant to the endorsement of new and radical ideas. Shermer’s main point here is to establish that Wallace possessed a “heretic personality”—one that shaped almost every aspect of his scientific work. “Traits usually trump states,” Shermer writes about the relative influence of internal (and largely psychological) and external (or largely social) factors in history.

More ambitious still is Shermer’s attempt to resolve the enigma of Wal- lace’s unconventional scientific thinking, using what he calls the Historical Matrix Model, which seeks to formalize the conviction that no single influence is sufficient to explain Wallace’s thinking about evolution. Rather, Wal- lace’s increasingly unconventional ideas are said to have been shaped by multiple causes interacting with one another and working in an “autocatalytic feedback loop” (whereby thought led Wallace to scientific evidence that in turn influenced his thought in a continuous loop).

Foremost among these influences was Wallace’s heretic personality, which Shermer explores using ideas and findings drawn, in part, from my own research on revolutionary scientists.10 To this component of his biographical model, Shermer adds what he calls Wallace’s penchant for “hyperselectionism,” as well as his receptivity to spiritualism, which had become a fashionable craze by the mid-1860s, when Wallace came under its spell. Wallace’s hyperselectionism can be seen in his belief that every trait must have an adaptive purpose (owing to natural selection), a view that caused him to reject much of Darwin’s theory of sexual selection, developed by Darwin to explain seemingly nonadaptive traits like the peacock’s tail. In this connection, Wallace was proud to portray himself as being a stronger defender of natural selection (and hence of “Darwinism”) than Darwin himself, who increasingly modified his original theory of evolution after 1859 to include alternative mechanisms.

Because Wallace believed that virtually all traits are adaptive but that primitive humans had no need for higher mathematical and other cognitive skills, he left himself open to the allure of spiritualism, which—befitting the overly trusting and even gullible features of his personality—allowed him to be duped by the wily mediums of his day. Wallace increasingly concluded that unseen cosmic forces were the next great unexplored frontier of natural science. Quite independently of his Historical Matrix Model, which includes other conceptual components besides the ones I have highlighted here, Shermer is persuasive in showing how Wallace’s personality and the peculiar mix of his “borderland” scientific interests (particularly mesmerism and phrenology) combined to make him vulnerable to a host of other unorthodox viewpoints, such as his ardent campaign against vaccination and his strong commitment to socialist causes. At the same time, Shermer’s analysis helps us to understand how Wallace’s heretic personality permitted this highly unconventional thinker to endure, with surprising nonchalance, the considerable ostracism of his scientific peers.

I have been able to convey only the general flavor of Shermer’s blend of history and science—which includes ideas drawn from psychology, sociology, statistics, game theory, and even chaos theory—in constructing his overall biography. Most of what Shermer accomplishes in his biography, however, is not achieved through full-blown science but rather through the application of ideas and techniques drawn from science. In this regard, Shermer is flexibly true to Darwin’s dictum, even if he is also, for the most part, practicing the art of biography in its traditional form.

One is tempted to wonder what both Darwin and Wallace would have thought about Shermer’s provocative attempt at a scientific approach to biography. I suspect they would both have been intrigued and generally supportive. After all, Darwin once considered doing a study on the subject of scientific creativity, and he was also the first person to really show that history could be treated as a science. In addition, Dar- win was intensely interested in biography, and both he and Wallace wrote autobiographies in an effort to understand the sources of their own achievements. As Shermer has also reminded us, both men fully appreciated that theories ultimately dictate how we perceive the world. Biographers hold theories too, and it is to Shermer’s credit that he articulates his own theoretical assumptions more boldly and explicitly than other biographers are generally willing to do. At the same time, Shermer has convincingly shown us that the man who has long resided in Darwin’s shadow, as his ever-modest doppelgänger, was a fiercely independent thinker in his own right and someone who actually succeeds in making Darwin look like a scientific conservative.